Landscape Vegetation Cover Research Articles

Natural and anthropogenic factors influence on the botanic natural sanctuary vegetation cover dynamics of the river Volga delta

The river Volga state assessment and landscape functioning is an extremely necessary part for stable and ecologically safe region development. One of the most important this assessment components is vegetation monitoring organization and conduction, which is the necessary part of modern ecosystem exploitation. Monitoring investigations brief results of the botanic natural monuments vegetation cover situated in the eastern part of the river Volga delta are shown in this work. Environment major factors change impact defining main ecological properties if deltoid landscape vegetation cover: some climatic characteristics, the river Volga hydrological regime changes and flooding conditions, vegetation cover differentiation peculiarities in dependence on deltoid land forms and confined processes to it are considered for the monitoring period. It was revealed during the monitoring that abrupt water-soluble salts amount increase in soils occurred, also toxicity level and soil salinization type from chloride- sulfate to sulfate-chloride, that affects vegetation cover: total biomass decrease, projective cover degree decrease on the all deltoid landscape high level, sedges and gramineous plant involvement degree decrease and herbs increase in vegetation cover due to ariditization degree and desert advancing caused either by natural or anthropogenic impact.

High‐productivity vegetation is important for lessening bird declines during prolonged drought

Abstract Locations in which ecological assemblages show high resistance to climate pressures, such as drought, are likely to be important refuges for biota in changing climates. We asked whether environmental characteristics of locations were associated with the capacity of bird assemblages to withstand prolonged drought. We used a multispecies index to quantify trends in bird assemblages during a 13‐year drought at >500 locations (>18,000 surveys) in the Murray–Darling Basin, south‐eastern Australia, using data from the Atlas of Australian Birds. We investigated whether the resistance of bird assemblages was associated with (1) vegetation structure; (2) vegetation productivity (vegetation greenness); (3) landscape context (patch size, landscape vegetation cover); or (4) physical environment (elevation, terrain, topography, availability of surface water). Vegetation productivity, measured by vegetation greenness (Normalized Difference Vegetation Index), was the only potential predictor with strong evidence of an effect, and was positively associated with the index of drought resistance. There was little evidence that variables characterizing landscape context, vegetation structure or the physical environment of sites were associated with drought resistance of bird communities. Synthesis and applications. Bird assemblages in locations with high vegetation greenness are more resistant to severe drought. Prioritizing conservation investments in areas with locally high vegetation productivity is likely to be an effective strategy for increasing the resistance of bird assemblages to extreme drought, especially in areas where mean productivity is relatively low, such as arid and semi‐arid regions. Remotely sensed vegetation greenness may be a promising source of information for identifying drought refuges for birds and possibly other biota.

Assessment of geostatistical features for object-based image classification of contrasted landscape vegetation cover

Accurate mapping and monitoring of savanna and semiarid woodland biomes are needed to support the selection of areas of conservation, to provide sustainable land use, and to improve the understanding of vegetation. The potential of geostatistical features, derived from medium spatial resolution satellite imagery, to characterize contrasted landscape vegetation cover and improve object-based image classification is studied. The study site in Brazil includes cerrado sensu stricto, deciduous forest, and palm swamp vegetation cover. Sentinel 2 and Landsat 8 images were acquired and divided into objects, for each of which a semivariogram was calculated using near-infrared (NIR) and normalized difference vegetation index (NDVI) to extract the set of geostatistical features. The features selected by principal component analysis were used as input data to train a random forest algorithm. Tests were conducted, combining spectral and geostatistical features. Change detection evaluation was performed using a confusion matrix and its accuracies. The semivariogram curves were efficient to characterize spatial heterogeneity, with similar results using NIR and NDVI from Sentinel 2 and Landsat 8. Accuracy was significantly greater when combining geostatistical features with spectral data, suggesting that this method can improve image classification results.

Use of restored habitat by rainforest birds is limited by spatial context and species’ functional traits but not by their predicted climate sensitivity

Active restoration of biodiverse forest uses significant resource investment to produce rapid partial recovery of biodiversity, but with unknown longer term outcomes. Here we test the capacity of intensive high diversity rainforest restoration plantings to develop forest-like bird communities beyond their first decade of growth. Across a network comprising 16 such plantings aged 10–24years and eight old growth rainforest reference sites, spread across about 700km2 in the Australian Wet Tropics, we measured bird community composition and 18 attributes related to the sites’ local and landscape vegetation cover and other spatial properties. We compiled additional information on the bird species’ habitat use, movement patterns, responses to edges between forest and cleared land, and expected climate sensitivities. Data analyses showed that bird communities in restoration plantings did not become more similar to those of reference rainforest during their second decade of development. Across replanted sites, occupancy by bird species was significantly predicted by their functional traits, being least among rainforest-dependent species that were also either endemic or sedentary edge-avoiders. Occupancy by rainforest-dependent species was least when nearby remnant rainforest cover (within 200m) was lowest. Species predicted to be climate-sensitive occupied restored habitat at similar rates to other species. These findings provide a foundation for better spatial planning for both habitat-focused and species-focused restoration, and show that expectations based on promising early outcomes of intensive forest restoration projects must be tempered with awareness of likely longer term limitations, highlighting the need to set realistic restoration goals.

A Study of Variation in Physiognomic Characteristics of Guinea Savanna Vegetation

Variation in structural composition of Guinea savannah vegetation was investigated in Kpashimi forest reserve, Niger State, Nigeria. Field work inventory was conducted to determine the current status of the vegetation physiognomic characteristics of the six physiographic units in the study area; comprising of Riparian Forest, Savannah Woodland, Degraded forest Scrubland, Grassland, and Bare surface. Parameters measured include tree density, trunk diameter, basal area, tree density, tree species diversity, tree height, crown cover, shrub cover, and grass cover. The aim of the study is to determine and compare the variation in structural characteristics of the vegetation of the study area. Analysis of variance (ANOVA) showed significant differences amongst virtually all the parameters among the physiographic units. In general, the landscape of the forest reserve has been influenced significantly by anthropogenic disturbance and the resulting landscape vegetation cover is a mixture of natural and human managed mosaics that vary in shape, size, structure and arrangement. Thus, drastic measures need to be taken so as to reverse the trend and to mitigate the far reaching ecological consequences of vegetation degradation as highlighted in this study. Access to UNFCC carbon credit is hereby recommended for the management of the study area.

Is there an ecological basis for species abundance distributions?

Community ecologists have attempted to explain species abundance distribution (SAD) shape for more than 80 years, but usually without relating SAD shape explicitly to ecological variables. We explored whether the scale (total assemblage abundance) and shape (assemblage evenness) of avifaunal SADs were related to ecological covariates. We used data on avifaunas, in-site habitat structure and landscape context that were assembled from previous studies; this amounted to 197 transects distributed across 16,000 km(2) of the box-ironbark forests of southeastern Australia. We used Bayesian conditional autoregressive models to link SAD scale and shape to these ecological covariates. Variation in SAD scale was relatable to some ecological covariates, especially to landscape vegetation cover and to tree height. We could not find any relationships between SAD shape and ecological covariates. SAD shape, the core component in SAD theory, may hold little information about how assemblages are governed ecologically and may result from statistical processes, which, if general, would indicate that SAD shape is not useful for distinguishing among theories of assemblage structure.

Beyond the Fragmentation Threshold Hypothesis: Regime Shifts in Biodiversity Across Fragmented Landscapes

Ecological systems are vulnerable to irreversible change when key system properties are pushed over thresholds, resulting in the loss of resilience and the precipitation of a regime shift. Perhaps the most important of such properties in human-modified landscapes is the total amount of remnant native vegetation. In a seminal study Andrén proposed the existence of a fragmentation threshold in the total amount of remnant vegetation, below which landscape-scale connectivity is eroded and local species richness and abundance become dependent on patch size. Despite the fact that species patch-area effects have been a mainstay of conservation science there has yet to be a robust empirical evaluation of this hypothesis. Here we present and test a new conceptual model describing the mechanisms and consequences of biodiversity change in fragmented landscapes, identifying the fragmentation threshold as a first step in a positive feedback mechanism that has the capacity to impair ecological resilience, and drive a regime shift in biodiversity. The model considers that local extinction risk is defined by patch size, and immigration rates by landscape vegetation cover, and that the recovery from local species losses depends upon the landscape species pool. Using a unique dataset on the distribution of non-volant small mammals across replicate landscapes in the Atlantic forest of Brazil, we found strong evidence for our model predictions - that patch-area effects are evident only at intermediate levels of total forest cover, where landscape diversity is still high and opportunities for enhancing biodiversity through local management are greatest. Furthermore, high levels of forest loss can push native biota through an extinction filter, and result in the abrupt, landscape-wide loss of forest-specialist taxa, ecological resilience and management effectiveness. The proposed model links hitherto distinct theoretical approaches within a single framework, providing a powerful tool for analysing the potential effectiveness of management interventions.

Impact of an Ecohydrology Classroom Activity on Middle School Students’ Understanding of Evapotranspiration

Current trends in ecological research emphasize interdisciplinary approaches for assessing effects of present and predicted environmental changes. One such emerging interdisciplinary field is the discipline of ecohydrology, which studies the feedbacks and interactions between ecological and hydrological processes. However, interdisciplinary science, which includes ecohydrology and other fields, has not yet been effectively translated into many K–12 curricula. We adapted an ecohydrological research project, originally conducted at the Biosphere 2 research apparatus, for use in a middle school classroom. The experiment focuses on describing the effects of changes in landscape vegetation cover on the partitioning of evapotranspiration, the major component of the water budget, into plant transpiration and soil evaporation. The 1‐week long experiment was conducted by Grade 6 students (n = 82) in classrooms in Oro Valley, AZ. Students completed pre‐ and post‐experiment tests designed to assess their general understanding of the components of evapotranspiration as well as the scientific procedures that can be used to differentiate them. Our results show significant improvement between the pre‐ and post‐experiment evaluations on the understanding of the water cycle concepts, particularly those associated with evapotranspiration. This improvement illustrates how the incorporation of experimental knowledge can constitute a key instrument to successful delivery of scientific information in the classroom. We discuss how current scientific research can be effectively incorporated into the science curriculum, which in turn can be used as an instrumental tool to produce scientifically relevant data.

Quantifying spatial heterogeneity at the landscape scale using variogram models

The monitoring of earth surface dynamic processes at a global scale requires high temporal frequency remote sensing observations which are provided up to now by moderate spatial resolution sensors. However, the spatial heterogeneity within the moderate spatial resolution pixel biases non-linear estimation processes of land surface variables from remote sensing data. To limit its influence on the description of land surface processes, corrections based on the quantification of the intra-pixel heterogeneity may be applied to non-linear estimation processes. A complementary strategy is to define the proper pixel size to capture the spatial variability of the data and minimize the intra-pixel variability. This work provides a methodology to characterize and quantify the spatial heterogeneity of landscape vegetation cover from the modeling of the variogram of high spatial resolution NDVI data. NDVI variograms for 18 landscapes extracted from the VALERI database show that the land use is the main factor of spatial variability as quantified by the variogram sill. Crop sites are more heterogeneous than natural vegetation and forest sites at the landscape level. The integral range summarizes all structural parameters of the variogram into a single characteristic area. Its square root quantifies the mean length scale (i.e. spatial scale) of the data, which varies between 216 and 1060 m over the 18 landscapes considered. The integral range is also used as a yardstick to judge if the size of an image is large enough to measure properly the length scales of the data with the variogram. We propose that it must be smaller than 5% of the image surface. The theoretical dispersion variance, computed from the variogram model, quantifies the spatial heterogeneity within a moderate resolution pixel. It increases rapidly with pixel size until this size is larger than the mean length scale of the data. Finally based on the analysis of 18 landscapes, the sufficient pixel size to capture the major part of the spatial variability of the vegetation cover at the landscape scale is estimated to be less than 100 m. Since for all the heterogeneous landscapes the loss of NDVI spatial variability was small at this spatial resolution, the bias generated by the intra-pixel spatial heterogeneity on non-linear estimation processes will be reduced.